The Modern Heat Flow Database of Norway and its Implications for Geothermal Energy

The Geological Survey of Norway is conducting the largest heat flow study in Norway ever carried out since the 1970s. In the framework of the Kontiki and HeatBar projects, we measured temperatures in 17 drillholes located in most regions of Norway mainland. In contrast with previous heat flow studies, most of our drillholes reach depths exceeding 800 m, allowing for correcting geothermal gradients for paleoclimatic effects and for estimating deep underground temperatures. The data were primarily used to calculate the relative amount of heat flow produced in the different units of the Norwegian basement and to extrapolate this information to the offshore areas. In addition, using the calculated heat flow values, recently published thermal properties of rocks in Norway and results from previous geological and geophysical studies, we computed underground temperatures at different depths. Relatively low temperatures are predicted down to 5 km in central and northern Norway, restricting the geothermal potential of these regions to the use of "low temperature fields" (i.e. < 100°C) but for the Oslo Region, the most populated region of Norway, our calculations suggest more favourable conditions. These preliminary findings need to be confirmed by more focused studies.